There has been a desire in the area of diaper fabrication to provide a web for use in diaper fabrication which is (1) elastic over its entire surface--to provide a tight yet comfortable fit; (2) water repellent--to retain fluid materials within the confines of the diaper; (3) breathable--to allow an exchange of vapors through the diaper material; (4) soft--for improved comfort and (5) inexpensive to manufacture--so that that diaper may be economically marketed to the consumer.
Unfortunately, the known nonwoven materials which have, to date, been marketed have been lacking in one or more of these characteristics. Furthermore, these nonwoven materials have generally been formed from elastomeric materials and have not been formed by utilization of the novel and economical processes of the present invention.
For example, U.S. Pat. No. 2,957,512 to Wade discloses a method for producing an elastic composite sheet material in which a creped or corrugated flexible sheet material is bonded to, for example, an elastic meltblown material. It is stated at column 4, lines 60-65 of the patent that in formation of the structures illustrated in FIGS. 2-6 the elastomeric material is maintained in a relaxed condition during the bonding. At column 5, lines 39-48, it is stated that the fibrous web of elastomeric material may be stretched and bonded to the corrugated web at spaced points or areas and, upon allowing the fibrous elastomeric web to relax, the composite web will assume the structure illustrated in FIG. 7.
Yet another method for forming a composite elastic fabric is disclosed in U.S. Pat. No. 3,316,136 to Pufahl. The preferred method of fabrication of this fabric involves the utilization of an adhesive which is first applied in a predetermined pattern to an elastic backing material and the elastic backing material is then stretched to an elongated state. While the elastic material is in the stretched, elongated state an overlying fabric is placed in contact therewith and held in pressurized engagement with the elastic material for a time period sufficient to insure adhesion of the two layers. Thereafter, upon drying of the applied adhesive, the tension on the elastic backing material is released causing the overlying fabric to gather in the areas outlined by the adhesive.
U.S. Pat. No. 3,485,706 to Evans at example 56 discloses the fabrication of an elongatable nonwoven, multilevel patterned structure having elasticity in one direction from an initially layered material. The structure is composed of two webs of polyester staple fibers which have a web of spandex yarn located therebetween. The webs are joined to each other by application of hydraulic jets of water which entangle the fibers of one web with the fibers of an adjacent web. During the entanglement step of fabrication the spandex yarn is prestretched 200 percent.
U.S. Pat. No. 3,673,026 to Brown discloses a method for manufacturing a laminated fabric and specifically discloses a method for manufacturing a nonwoven laminated fabric of controlled bulk. In this method separate webs of nonwoven material, e.g. creped tissue or bonded synthetic fiber, are elastically stretched to different degrees of elongation and laminated by bonding to one another while in their differentially stretched states. The bonded webs are thereafter relaxed so as to produce different degrees of contraction in each web with resultant separation of the webs in the unbonded regions and controlled bulk in the laminate. It is stated that the differential stretching includes the situation where only one web is actually stretched and the other web is maintained slack or nearly so.
U.S. Pat. No. 3,687,797 to Wideman discloses a method for producing a resilient cellulosic wadding product obtained by laminating a lower cellulosic wadding web to a prestretched polyurethane foam web. The process involves applying adhesive in a desired pattern to either of the webs with the wadding web then being laminated to the prestretched polyurethane foam web. During lamination of the wadding web to the polyurethane foam web the foam web is maintained in a stretched condition. After lamination of the two webs, the tension on the prestretched polyurethane foam web is released to cause a contraction of the foam web. The adhesive retains the wadding product and foam together while permitting bulking in areas between the adhesive zones. The stresses still remaining in the product after contraction may be further relieved by wetting.
U.S. Pat. No. 3,842,832 to Wideman is directed to a disposable stretch product such as a bandage and a method for production of the product. The product is manufactured by passing a longitudinally oriented nonwoven material over a roller so as to apply an adhesive to one surface of the nonwoven material. At the same time a polyurethane web is heated and longitudinally stretched and adhered to the nonwoven material. Thereafter, a second nonwoven material is adhered to the other surface of the polyurethane web to form a laminate consisting of a stretched inner polyurethane core and outer unstretched nonwoven fabric layers adhered to the core by the adhesive. Next, the laminate is passed through a moistening device which results in a relaxing of the engagement between the nonwoven fabric outer layers and the adhesive connecting the outer layers to the stretched polyurethane core layer. This allows the stretched polyurethane layer to return to substantially its original length which results in the outer nonwoven layers being buckled or undulated to form wrinkles.
U.S. Pat. No. 4,104,170 to Nedza discloses a liquid filter having an improved extended polypropylene element. Fabrication of the polypropylene element is accomplished by forming a spunbonded underlayer of a continuous polypropylene fiber which adheres to itself as it is laid down in a random pattern. Thereafter, an overlayer of short polypropylene fibers is deposited onto the underlayer by, for example, meltblowing the overlayer onto an extended sheet of the underlayer.
A method for producing an elastic cloth structure which includes fibers of a synthetic, organic, relatively elastomeric polymer and fibers of a synthetic, organic, elongatable, but relatively nonelastic polymer is disclosed in U.S. Pat. No. 4,209,563 to Sisson. The method includes the steps of forwarding the relatively elastic fibers and elongatable but relatively non-elastic fibers for a well dispersed random lay-down on a porous forming surface of an unbonded web having random fiber crossings. Thereafter, at least some of the fiber crossings are bonded to form a coherent bonded cloth web which is stretched to elongate some of the fibers in at least one direction and then released so that retraction of the web by the relatively elastomeric fibers provides for looping and bunching of the elongatable relatively nonelastic fibers. Forwarding of the fibers to the porous forming surface is positively controlled, and this positive control is contrasted at column 7, lines 19-33 of the patent to the use of air streams to convey the fibers. It is also stated at column 9, line 44 et. seq. of the patent that bonding of the filaments to form the coherent cloth may utilize embossing patterns or smooth heated roll nips.
U.S. Pat. No. 4,296,163 to Emi et al. discloses a fibrous composite having a coalesced assembly of (A) a sheet-like mesh structure composed of fibers of a synthetic elastomeric polymer, the individual fibers of which are interconnected at random in irregular relationship to form a number of meshes of different sizes and shape with the mesh structure having a recovery ratio after 10% stretch of at least 70% in two arbitrarily selected, mutually perpendicular directions on the plane of the mesh structure, and (B) a mat-, web- or sheet-like fiber structure composed of short or long fibers, with the fiber structure having a recovery ratio after 10% stretch of less than 50% in at least one arbitrarily selected direction. It is stated that the elastic composite is suitable as various aparrel base materials and industrial materials such as filter cloths, adsorbents and heat insulating materials. Methods for forming the composite are described at column 6, line 64 et seq. and these methods include spun bonding, see column 9, lines 15-41.
U.S. Pat. No. 4,323,534 to DesMarais discloses an extrusion process for a thermoplastic resin composition for fabric fibers with exceptional strength and good elasticity. At column 8 under the subtitle "Fiber-Forming" meltblowing of a compounded resin comprising 79.13% KRATON G-1652, 19.78% stearic acid, 0.98% titanium dioxide and 0.1% Irganox 1010 antioxidant is disclosed. It is stated that individual fibers were extruded from the meltblowing die.
U.S. Pat. No. 4,355,425 to Jones discloses a panty with a built-in elastic system to minimize gathering and to provide a comfortable, conforming fit and a method for assembling the panty. It is stated that a material made of meltblown KRATON rubber is well suited for the panty fabric material. It is also stated that a process for making meltblown KRATON fabrics is disclosed and shown schematically in FIG. 8 of the patent. The process which appears to utilize KRATON G-1652 is discussed starting at column 4, line 67 of the patent.
U.S. Pat. No. 4,379,192 to Wahlquist discloses a method for forming an impervious absorbent barrier fabric embodying film and fibrous webs where one or more meltblowing dies meltblow discontinuous fibers of small diameter as a mat directly on a prebonded web of continuous filaments. At column 3, lines 35-40 of the patent it is stated that by forming the microfiber mat directly onto the prebonded continuous filament web, primary bonds are created between the microfibers and the continuous filaments which attach the microfiber mat to the continuous filament web.
U.S. Pat. No. 4,426,420 to Likhyani discloses hydraulically entangled spunlaced fabrics composed of at least two types of staple fibers and processes for their formation which include heat treating elastomeric fibers, which behave as ordinary staple fibers until they are heat treated, to impart improved stretch and resilience properties to the fabric. The method includes the steps of drawing a potentially elastomeric fiber and allowing it to relax between the drawing and wind-up steps.
U.S. Pat. No. 4,446,189 to Romanek discloses a nonwoven textile fabric laminate which includes at least one layer of nonwoven textile fabric which is secured by needle punching to an elastic layer so that the nonwoven layer of textile fabric will be permanently stretched when the elastic layer is drafted within its elastic limits. When the elastic layer is allowed to relax and return to substantially its condition prior to being drafted the nonwoven fabric layer is stated to exhibit increased bulk as a result of its concurrent relaxation. It is also stated that the nonwoven textile fabric laminate may be utilized to form wearing apparel which has enhanced freedom of movement.
The abstract of Japanese document No. 47-43150 discloses a method for producing a nonwoven fabric having high tenacity with the method being carried out by (a) monaxially stretching a sheet or film made of a mixture of incompatible polymers, (b) laminating this sheet or material with a layer of foamed polymer, (c) stretching the laminate at right angles to the direction of orientation of the substrate and then (d) stretching in the direction orientation of the substrate. Preferred polymers are stated to include polyamides, linear polyesters, and polyolefins. Preferably, the upper layer is a polypropylene foam.
A Shell Chemical Company brochure entitled "KRATON Thermoplastic Rubber" generally discusses thermoplastic KRATON materials. This brochure is code designated by "SC: 198-83 printed in U.S.A. 7/83 SM".
While the above-discussed documents may disclose products and processes which exhibit some of the characteristics or method steps of the present invention none of them discloses or implies (a) the presently claimed processes for forming a gathered nonwoven web from nonelastic materials where the thus-formed gathered web possesses elastic characteristics or (b) the gathered nonwoven elastic webs resulting from these processes.